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Seals for Bearing

Seals for Bearing

(OP)
Hey guys,

I'm looking for some bearings that would work as a seal... or if you guys know any workarounds, please let me know. Here's what I have so far:

I have a rectangular tank (2.3L max, low pressure). This will be filled up with liquid such as water and oil.
I have a rotating shaft that will go through the tank in one end, and out the other (horizontally). The shaft will be submerged.
For each end of the shaft, I need a bearing in order to keep the rod spinning, with minimal friction as possible.

The problem s that bearings don't work as a mechanical seal, and vice versa. So that's where I am at the moment - how do they fit together? Mechanical cartridge seals and the bearings? Are these the stuff I should be looking at, or are there other things too?

Kindly let me know.

Thanks all!

RE: Seals for Bearing

Just buy ball bearings with seals.

Be sure to check with your bearing seller about the nature of the seals. The things they call 'labyrinth seals' or 'noncontact seals' are not actual seals.

You want 'lip seals', the old fashioned kind, that will keep the grease in the bearing, and keep most things out.


Mike Halloran
Pembroke Pines, FL, USA

RE: Seals for Bearing

You do want to use a separate seal apart from the bearing seal. No dynamic seal is absolutely leak-proof and bearings will be destroyed by contamination. Lips seals or mechanical seals can be used. The bearing takes the mechanical loads and keeps the shaft centered in the other seal. There needs to be a drain or vent between the seal and bearing. Pay attention to the direction of sealing. Lip seals will seal in only one direction. Back-to-back lip seals will seal in both.

RE: Seals for Bearing

A sealed-for-life ball bearing should provide somewhere between poor and adequate sealing. No shields or bearing isolators though - those do not have contacting lips to contain liquid.

I would probably skip that and put a separate oil seal on each end. Not a typical lip seal though - I would use a teflon lip seal or isomag if the liquid will be normally above the seal lip.

David

RE: Seals for Bearing

This is a common problem for the bottom auger in API separators. Ours use a non-metallic bushing with a simple grease seal. Our newest API was made by Siemens. An internet search should find what you need.

Johnny Pellin

RE: Seals for Bearing

Given the low head, a Forsheda v-ring seal inside the tank will probably be more than adequate. Even better, they are cheap and do not require the sort of machined socket that a cartridge seal does.

Mike Halloran
Pembroke Pines, FL, USA

RE: Seals for Bearing

How long must this rig last?

You'll need some type of self aligning bearing, or just make the tank wall real flimsy and mount the bearings to it.

Will the tank sit full but idle for extended periods?

RE: Seals for Bearing

(OP)
Thank you Mike, compositepro, geesamand, JJPellin and Tmoose all for the answers.

As for the duration of a test, it's currently undecided, but there are no plans to have it go on for extended periods of time. A rough estimate would be 5 minutes for each test. After a test, the liquid will be drained, and filled up with another type of liquid. There are no plans to have the tank full and idle, so no.

I'm looking up a lot of the stuff you guys mentioned.

I contacted McMaster-Carr the other day, about double-lip seals. They say lip seals are not reliable for submerged applications. Could work, but not guranteed nor recommended. Do you guys know otherwise?

RE: Seals for Bearing

(OP)
EDIT: Contacted McMaster-Carr about double-sealed bearings, not double-lip seals.

Should have previewed before submitting post.

RE: Seals for Bearing

If the unspecified liquids are toxic or otherwise acutely dangerous, then you need serious seals.

If your tests will be ruined by a tiny amount of carryover or axial contamination, as in a little test fluid leaks into the bearing and then leaks out of the bearing into a subsequent test, then you need serious seals.

If not, the radial lip seals in ball bearings will work long enough for a five minute test. ... and if you've used 20x series or other inexpensive ball bearings and made them easy to replace, you can just slap new ones in when the second seal fails.

So far, you haven't specified running conditions that would exclude any sort of ball bearing, or indeed any sort of bearing, or no bearing at all.

Mike Halloran
Pembroke Pines, FL, USA

RE: Seals for Bearing

I would suggest a different design aspect (if possible). Incorporating a double seal ((o-ring or t-seal) configuration that would accomplish the task of allowing the shaft to rotate with minimal to no leakage. Meaning: Have the shaft go through the t-seal or o-ring configuration and then putting the bearing to allow for rotation. Good luck

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